Coating apparatus

Abstract

A coating apparatus having an extrusion type coating head to form a coating on the surface of a support by extruding a coating liquid continuously or successively from a slit, wherein the slit is tapered so as to expand or become wider gradually from its inlet end so as to allow the coating liquid to be extruded toward its outlet end and apply the coating liquid onto the surface of the support and wherein an opening slit width (d1) at the inlet end of the slit and an opening slit width (d2) at the outlet end thereof satisfies the following relations: 5% ≦[(d2-d1)/d1]×100≦20%. The arrangement of the slit can form a coating in a uniform film thickness by preventing the occurrence of irregularities or streaks on the surface of the coating or by suppressing a variation in film thickness.

What is claimed is: 
     
       1. A coating apparatus, which comprises an extrusion coating head disposed to coat a surface of a support with a coating liquid by extruding the coating liquid continuously or successively from a slit formed between opposite inner walls of the coating head, wherein the slit is tapered so as to become wider gradually from an inlet end thereof to an outlet end thereof and allow the coating liquid to be extruded toward the outlet end of the slit, through which the coating liquid is applied onto the surface of the support and wherein an opening slit width (d1) at the inlet end of the slit and an opening slit width (d2) at the outlet end thereof satisfies the following relations:   5%≦[(d2-d1)/d1]×100≦20%.     2.   
     
     
       2. The coating apparatus as claimed in claim 1, wherein said opening slit width (d1) and said opening slit width (d2) satisfies the following relations:   7%≦[(d2-d1)/d1]×100≦15%.     
     
     
       3. The coating apparatus as claimed in claim 2, wherein said opening slit width (d1) at the inlet end of the slit is from 0.05 mm to 0.2 mm. 
     
     
       4. The coating apparatus as claimed in claim 2, wherein said opening slit width (d1) at the inlet end of the slit is set to be from 0.1 mm to 0.16 mm. 
     
     
       5. The coating apparatus as claimed in claim 1, wherein said opening slit width (d1) at the inlet end of the slit is from 0.05 mm to 0.2 mm. 
     
     
       6. The coating apparatus as claimed in claim 1, wherein said opening slit width (d1) at the inlet end of the slit is set so as to be from 0.1 mm to 0.16 mm.